Our main objective is to describe the events that occur during the formation of specific connections in the primate visual system and to elucidate the mechanisms that regulate developmental specificity. First, to gain insight into the cues that play a role in sorting out the crossed retinal axons from the uncrossed axons, we investigated the sequence of their initial ingrowth in rhesus monkey embryos. Our results show that their is an orderly and sequential ingrowth of these pioneer retinal axons indicating that specific chiasmatic cues are expressed early in development. Second, we are currently using confocal microscopy to examine the initial innervation of the lateral geniculate nucleus by retinal afferents.